20,457 research outputs found
Microwave conductivity of heavy fermions in UPd2Al3
Heavy-fermion compounds are characterized by electronic correlation effects
at low energies which can directly be accessed with optical spectroscopy. Here
we present detailed measurements of the frequency- and temperature-dependent
conductivity of the heavy-fermion compound UPd2Al3 using broadband microwave
spectroscopy in the frequency range 45 MHz to 40 GHz at temperatures down to
1.7 K. We observe the full Drude response with a relaxation time up to 50 ps,
proving that the mass enhancement of the heavy charge carriers goes hand in
hand with an enhancement of the relaxation time. We show that the relaxation
rate as a function of temperature scales with the dc resistivity. We do not
find any signs of a frequency-dependent relaxation rate within the addressed
frequency range.Comment: 14 pages, 4 figure
Global and uniqueness properties of stationary and static spacetimes with outer trapped surfaces
Global properties of maximal future Cauchy developments of stationary,
m-dimensional asymptotically flat initial data with an outer trapped boundary
are analyzed. We prove that, whenever the matter model is well posed and
satisfies the null energy condition, the future Cauchy development of the data
is a black hole spacetime. More specifically, we show that the future Killing
development of the exterior of a sufficiently large sphere in the initial data
set can be isometrically embedded in the maximal Cauchy development of the
data. In the static setting we prove, by working directly on the initial data
set, that all Killing prehorizons are embedded whenever the initial data set
has an outer trapped boundary and satisfies the null energy condition. By
combining both results we prove a uniqueness theorem for static initial data
sets with outer trapped boundary.Comment: 38 pages, 2 figures, Late
Strange and charm meson masses from twisted mass lattice QCD
We present first results of a 2+1+1 flavor twisted mass lattice QCD computation of strange and charm meson masses. We focus on D and D_s mesons with spin J = 0,1 and parity P = -,+
On the use of reference points for the biobjective Inventory Routing Problem
The article presents a study on the biobjective inventory routing problem.
Contrary to most previous research, the problem is treated as a true
multi-objective optimization problem, with the goal of identifying
Pareto-optimal solutions. Due to the hardness of the problem at hand, a
reference point based optimization approach is presented and implemented into
an optimization and decision support system, which allows for the computation
of a true subset of the optimal outcomes. Experimental investigation involving
local search metaheuristics are conducted on benchmark data, and numerical
results are reported and analyzed
Practical inventory routing: A problem definition and an optimization method
The global objective of this work is to provide practical optimization
methods to companies involved in inventory routing problems, taking into
account this new type of data. Also, companies are sometimes not able to deal
with changing plans every period and would like to adopt regular structures for
serving customers
Some explicit Krein representations of certain subordinators, including the Gamma process
We give a representation of the Gamma subordinator as a Krein functional of
Brownian motion, using the known representations for stable subordinators and
Esscher transforms. In particular, we have obtained Krein representations of
the subordinators which govern the two parameter Poisson-Dirichlet family of
distributions
Investigation of the Role of Elastic Unitarity in High-Energy Scattering: Gribov's Theorem and the Froissart Bound
We re-examine V. Gribov's theorem of 1960 according to which the total
cross-section cannot approach a finite non-zero limit with, at the same time, a
diffraction peak having a finite slope. We are very close to proving by an
explicit counter-example that elastic unitarity in the elastic region is an
essential ingredient of the proof. By analogy, we raise the question of the
saturation of the Froissart-Martin bound, for which no examples incorporating
elastic unitarity exist at the present time.Comment: 11 pages, 1 figures, latex with sproc.st
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